Elastic and Mechanical Properties of Human Dentin

Abstract

THE elastic and mechanical properties of dentin were studied as early as 1895 by Black' who measured the compressive strengths of cubes of dentin and reported that a cube, 0.08 inch square, had an average compressive strength of 37,200 psi and an elastic deformation of 2.09 per cent when subjected to a load of 100 pounds (elastic modulus-0.8 x106 psi). Peyton, Mahler, and Hershenov2 reported average values of 23,400 psi, 36,100 psi, and 1.67 X106 psi for the proportional limit, compressive strength, and elastic modulus, respectively. Stanford, Paffenbarger, and Kumpula3 reported average values for these properties of 25,100 psi, 50,400 psi, and 4.1 x106 psi, respectively. Neumann and Di Salvo4 reported values from 1.1 to 1.7 X106 psi for the elastic modulus using large transverse sections of teeth. The values for the proportional limit and compressive strengths of dentin were in reasonable agreement, but those for the elastic modulus differed widely. The difficulties involved in handling small specimens of dentin and the problems connected with correcting the deformation used in the calculation of the elastic modulus values possibly account for the differences obtained in the various studies. It was felt that a critical re-evaluation of the technics and procedures used to obtain the elastic modulus, with particular emphasis on flow properties, would help to establish a better experimental value for the elastic modulus as well as the other physical properties of dentin. EXPERIMENTAL Equipment.-The equipment used to measure the elastic properties of dentin was the same as that described by Peyton, Mahler, and Hershenov,2 except for the compression testing machine and the type of steel plungers used. The stress was applied to the samples by a Riehle testing machine. The load scales of the testing machine were calibrated for loads in compression with a recently calibrated dynamometer ring. The calibration data for the 250 lb. scale, which was used for most of the measurements, showed that the load indicator was accurate to ± 0.5 per cent at the low end of the scale and to ± 0.1 per cent for the high portion of the scale. The actual error was generally ± 0.2 lb. over the entire scale. The accuracy on this and higher scales was greater than reading errors, and, therefore, the recorded scale readings were used directly in the calculation of the stress. This report represents the partial results of studies supported by Contract No. D-462

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